62 lines
1.5 KiB
Ruby
62 lines
1.5 KiB
Ruby
module TreeSpell
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# Changes a word with one of four actions:
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# insertion, substitution, deletion and transposition.
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class ChangeWord
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# initialize with input string
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def initialize(input)
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@input = input
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@len = input.length
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end
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# insert char after index of i_place
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def insertion(i_place, char)
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@word = input.dup
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return char + word if i_place == 0
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return word + char if i_place == len - 1
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word.insert(i_place + 1, char)
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end
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# substitute char at index of i_place
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def substitution(i_place, char)
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@word = input.dup
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word[i_place] = char
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word
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end
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# delete character at index of i_place
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def deletion(i_place)
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@word = input.dup
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word.slice!(i_place)
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word
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end
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# transpose char at i_place with char at i_place + direction
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# if i_place + direction is out of bounds just swap in other direction
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def transposition(i_place, direction)
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@word = input.dup
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w = word.dup
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return swap_first_two(w) if i_place + direction < 0
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return swap_last_two(w) if i_place + direction >= len
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swap_two(w, i_place, direction)
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w
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end
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private
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attr_accessor :word, :input, :len
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def swap_first_two(w)
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w[1] + w[0] + word[2..-1]
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end
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def swap_last_two(w)
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w[0...(len - 2)] + word[len - 1] + word[len - 2]
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end
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def swap_two(w, i_place, direction)
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w[i_place] = word[i_place + direction]
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w[i_place + direction] = word[i_place]
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end
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end
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end
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